Canon and Nikon had to introduce a minimum set of lenses along with their new mirrorless cameras. Panasonic will adopt the same strategy but it can already use the 10 Leica lens already available. Moreover, with the Sigma alliance will have affordable lens asap: Sigma needs "simply" adapt their existing lens to the new mount.

Ok anyway no hurry to go with any new “system” as only few lenses will be available for a while from any camera maker.
Also no one have yet announced anything better than the GH5/S can deliver in term of codec, apart from Fuji with their XT-3 and Blackmagic with their BMPCC 4K.

There is just a bit of confusion in term of the camera line up roadmap. The Panasonic S1 and S1R is 4K60fps. But isn't Panasonic has the goal to create 8K camera by 2020 Summer Olympics in Japan? If they release S1 and S1R in 2019, would a 8K camera release in 2020? That seems to be too close in term of flagship camera roadmap. I don't think 3/4 sensor is capable of doing 8K, so I don't think they will put 8K on GH6. I'm just surprise the S1 and S1R doesn't do 8K as it could give RED for a run of competition.

I think full frame is going to bring many people back to some challenges
Huge domes for rectilinear lenses, depth of field issues and the likes for video
I think it will be great for still but for video the 2x crop and the small lenses of mft are better